Cleaning apparatuses for underwater cleaning of a bottom surface, for example of a swimming pool, are known. Essentially, they have a suction pump arranged on a chassis which can be moved to and fro, the suction pump permitting the sucking up of contaminants which have been deposited on the bottom of the pool. In a known construction of such a device (U.S. Pat. No. 4,154,680) a suction nozzle terminating in a suction slot which takes up the entire width of the cleaning apparatus is positioned on a chassis moved by caterpillar tracks. The suction nozzle tapers to an intake connection, which is connected to the suction pump intake. A cleaning brush is arranged on the end face of the suction slot of the suction nozzle and through it flows the liquid sucked up by the suction pump.
The suction nozzle arranged on the chassis leads to a significant increase in the overall constructional length of the cleaning apparatus. Furthermore, when the apparatus is immersed, the load is removed from the caterpillar tracks due to buoyancy, so that despite the relatively high weight of the cleaning apparatus it can slide on sloping floor portions.